<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>BFC</title>
    <style>
         .box1{
            width: 200px;
            height: 200px;
            background-color: #bfa;
            /* float: left; */
            overflow: hidden;
         }

         .box2{
             width: 200px;
             height: 200px;
             background-color: orange;
             /* 开启BFC 之后，元素不会被浮动元素覆盖，因此跑到边恒来 */
             overflow: hidden;

         }

         .box3{
             width: 100px;
             height: 100px;
             background-color: yellow;
             margin-top: 100px;
         }
    </style>
   
</head>
<body>
    <div class="box1">
        <div class="box3"></div>
    </div>
    <!-- <div class="box2"></div> -->
</body>
</html>